1. Technical Field
The present invention relates to a tubular burner which is provided with: a mixing tube having, at a rear end thereof, an inlet port into which a fuel gas and primary air flow; and a flame hole member which has a plurality of flame holes opening in the forward direction and which is adapted to be fitted into a front end region of the mixing tube.
2. Background Art
As this kind of burner, there is conventionally known one which is described in U.S. Pat. No. 5,186,620. In the burner as described therein, a flame hole member is made of a sintered metal of larger thickness. A plurality of flame holes which open in the forward direction are formed in the flame hole member so that a mixture of a fuel gas and primary air (hereinafter also referred to as air-gas mixture) is ejected from these flame holes for combustion.
In the above-mentioned conventional burner, a plurality of flame retention holes are formed around the periphery of the flame hole member at a circumferential distance from one another. Each of the flame retention holes is constituted by a groove that is formed in the peripheral surface of the flame hole member. By making smaller the groove depth at the rear portion of the groove, the velocity of ejection of the air-gas mixture out of the flame retention holes is lowered. As a result, the flame to be formed by the combustion of the air-gas mixture to be ejected from the flame retention holes becomes hard to be lifted off, thereby securing flame stability.
However, the above-mentioned conventional burner has a disadvantage in that the flame hole member is made of a sintered metal of higher material cost and, therefore, that the cost increases.